Saputangan via Setia...
https://goo.gl/maps/QZtxTE7w3kkg...
Locals usually park their car at the hill top (same level with the Dam) and walk from the gate of the dam to the inner forest reserve. You can also use the forest reserve trail to hike up to Penang Hill which should take you approximately 3 hours. Many hikers do this route on weekends.
No, it is illegal.
Senior-friendly if fit. Slightly steep in places but not slippery unless immediately after heavy rain. 2.8km circuit, allow 40-45 min. Usually quite cool (relatively) so that helps too.